1. Technical Field
This disclosure relates generally to an ignition coil for an internal combustion engine.
2. Background Art
For instance, Japanese Patent No. 4209400 discloses an ignition coil for internal combustion engines which is equipped with a primary and a secondary coil magnetically coupled together and a case in which the primary and secondary coils are disposed. The case has a tubular high-voltage tower which extends toward the front end of the case. The high-voltage tower has a high-voltage output terminal which is press-fit therein and works to output high-voltage, as developed by the secondary coil. The case is filled with resin material which is disposed around a base end (i.e., a rear end) of the high-voltage output terminal to hermetically seal the primary and secondary coils.
In assembling of the ignition coil, the high-voltage output terminal is press-fitted in the base end of the high-voltage tower before the resin material is packed in the case, thereby avoiding escape of the resin material into the high-voltage tower when the resin material is packed in the case. Specifically, the high-voltage output terminal is press-fitted into the high-voltage tower to create a hermetical seal between itself and the case.
The ignition coil, as taught in the above publication, has the metallic high-voltage output terminal press-fitted directly into the high-voltage tower, thus resulting in an increased risk of stress is exerted by the high-voltage output terminal on the high-voltage tower. This leads to concern about damage, such as breakage or cracking, to the high-voltage tower, which usually results in risk of a failure in operation of the ignition coil. In order to alleviate this problem, the high-voltage tower is designed to have an increased wall thickness, however, this makes it difficult to reduce the overall size of the ignition coil.